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This study examined the safety of one type of strength training for prepubescent males. Eighteen males (av erage age, 8.3 ± 1.2 years) participated in a 45 min/ session, three session/week, 14 week supervised strength training program with an attendance rate of 91.5%. Concentric work was done almost exclusively. KinCom analysis showed significant strength gain in this group (P < 0.05), while an age, sex, and activity matched control group did not gain strength.Safety was evaluated by injury surveillance, blood pressure and heart rate monitoring, scintigraphy, and creatine phosphokinase measurement. Effects on growth and development, flexibility, and motor perform ance were also investigated, as these are factors with an impact on sports injury occurrence.Results showed that in the short term, supervised concentric strength training results in a low injury rate and does not adversely affect bone, muscle, or epi physes ; nor does it adversely affect growth, develop ment, flexibility, or motor performance. As the safety question is multifaceted, this should not lead to the conclusion that strength training for prepubescents is uniformly safe. Further research is needed.

We investigated 56 families afflicted with malignant hyperpyrexia. One hundred and twenty-four individuals within these families had had an episode of malignant hyperthermia, of whom we saw seventy-two. Serum creatine phosphokinase (CPK) was statistically higher in affected individuals and in close relatives than in normal volunteers. The magnitude of the serum CPK elevations varied significantly between families. While in some families the serum CPK was clearly elevated in affected individuals, in other families the serum CPK was normal or only moderately or inconsistently raised. In these latter families serum CPK measurement was therfore of little or no value in identifying afflicted members. The incidence of musculoskeletal abnormalities was greater in affected individuals and in close relatives than in the general population. Thus, the concomitant individual belonging to a family known to be susceptible to malignant hyperthermia was a better indicator of the MH trait than was the presence of only one of these parameters. For reasons which we do not fully understand, MHS individuals were found to require fewer anaesthetics than normal persons. The incidence of MH crises within each family fell significantly following investigation, counselling, and issuance of Medic-Alert bracelets.